As is well known in the art, in circumstances where significant quantities of material are required to be moved in a vertical (or substantially vertical) direction and transversely relative to the vertical, the existing systems and methods have various disadvantages. These circumstances can arise in different situations involving various processes.
For example, at certain times, relatively large quantities of a catalyst are required to be delivered into a reactor vessel at a petroleum refinery, at an upper end of the reactor. The upper end may be approximately 200 to 300 feet above ground level.
As is well known in the art, the catalyst may be aluminum oxide (Al2O3), or zeolites, which are complex aluminosilicates, or the catalyst may be nickel-based or based on other materials. Typically, the catalyst is provided in the form of particulate matter, e.g., with a bulk density of 0.80 to 0.96 g/cm3 and an average particle size between about 1270 μm (0.05 inches) to about 3175 μm (0.125 inches). The catalyst is typically loaded over a period of five to seven days, approximately once every three years. The reactor operates between the loadings of the catalyst. After about three years of operation, the reactor's catalyst is removed and replaced.
It is very important to minimize the reactor's downtime. It is also important to minimize, to the extent practicable, the wear and abrasion to which the catalyst is subjected before it is released into the reactor vessel.
The catalyst typically is provided by its manufacturer in the form of particulate matter (as noted above) in special containers. In the prior art, the usual method of delivering the catalyst to the top of the reactor vessel is to use a crane to lift each container individually to the top of the reactor. The catalyst is dumped out of the container or otherwise released therefrom, and directed into a hopper positioned on top of the reactor vessel. Other materials (e.g., ceramic support material, and grading material) that are particulate matter may also be delivered to the reactor vessel in this way.
The traditional method has a number of disadvantages. First, the capacity of a crane is typically between about 10 tonnes per hour and about 15 tonnes per hour. However, the loader or bin at the top of the reactor typically has a capacity of about 30 tonnes per hour. This means that, to provide the capacity required while loading, at least two cranes are needed, resulting in substantial costs and increased risk. In view of the problems associated with operating two cranes in close proximity to each other, this is rarely done, with the result that the particulate matter is often loaded in practice at a rate below the capacity of the loader or bin at the top of the reactor. It is anticipated that the loader capacity may increase to approximately 60 tonnes per hour, and it is not clear how this capacity could be met by the prior art.
Second, the traditional method can be dangerous. Typically, the crane raises the container to a position above a hopper in which the load from the container is receivable. The hopper is located above the reactor, and is configured to control the flow of the particulate matter into the reactor. The hopper typically includes a lid or covering that is normally in place on the hopper, to prevent rain and snow from entering into the hopper. Generally, the covering is removed only to permit the particulate matter to be loaded into the hopper. After the covering is removed, the particulate matter may flow from the container into the hopper, under the influence of gravity.
Third, the crane is often unable to operate. In general, the crane cannot operate safely if winds are greater than 25 km/hour. Where winds are between 20 km/hour and 25 km/hour, whether the crane operates is at the crane operator's discretion. Those skilled in the art would appreciate that, even in a light breeze, a worker positioning the container above the hopper is at risk of potential pinch points. Because of these limitations, loading is often required to be shut down until weather conditions improve. The delays in loading the reactor vessel due to weather conditions are extremely costly.
There are other disadvantages. For instance, if precipitation is falling when the container is above the open hopper, then some of the precipitation inevitably falls into the catalyst, which is undesirable because it adversely affects the effectiveness of the catalyst. Also, using the traditional method, personnel are required to be located at the top of the reactor, and at least partially exposed to the weather, in order to open the hopper, and to position the container on the hopper.
Other methods of vertically (or substantially vertically) moving and delivering the catalyst to the top of the reactor vessel have been tried, e.g., chain, bucket, pneumatic and vacuum conveying. In general, these methods have the disadvantage that they tend to abrade and degrade the catalyst excessively. Mechanical reliability is also frequently an issue with these alternative methods.